Addition product of lactone-modified epoxy resin with polyphenol and amino compounds

ABSTRACT

A coating resin composition comprising, as a main component, an amino group-containing, modified epoxy resin derivative obtained by subjecting a hydroxyl group-containing epoxy resin having epoxy equivalent of 200-400 and a cyclic ester compound represented by the general formula (I) ##STR1## (R is a hydrogen atom or a methyl group and n is 3-6) to an addition reaction to obtain an addition product and then adding to the addition product a polyphenol compound and an amino group-containing compound.

This application is a continuation of now abandoned application Ser. No.327,119 filed Mar. 22, 1989.

The present invention relates to a novel coating resin composition, moreparticularly to a coating resin composition which is superior in thicklayer coatability (desired in cationic electrocoating), weatherability,corrosion resistance, flexibility, adhesion to substrate, etc.

As cationic electrocoating resin composition, there has generally beenknown a resin composition which is a combination of (a) anepoxy-polyamine resin obtained by the reaction of an epoxygroup-containing resin with a polyamine and (b) a blocked polyisocyanatecuring agent, as described in, for example, U.S. Pat. No. 3947339. Asthe above epoxy group-containing resin, there is ordinarily used, inview of the corrosion resistance of the final resin composition, apolymer of bisphenol A and there is practically used a modified epoxyresin obtained by partially introducing into an epoxy resin aplasticity-modifying agent such as soft polyester, polyether, polyamide,polybutadiene, butadiene-acrylonitrile copolymer or the like to allowthe epoxy resin to have plasticity.

Recently, in the field of electrocoating for automobile body orunderparts of body, there has been a strong request to develop anelectrocoating paint having high-build coatability and capable offorming a cured coating film superior in weatherability, corrosionresistance, flexibility, adhesion to substrate, etc. in view of filmappearance and properties.

In connection with the above request, when in the above mentionedmodified epoxy resin, the amount of the plasticity-modifying agent isincreased in order to endow the epoxy resin with the thick layercoatability required in cationic electrocoating, there is introducedinto the epoxy resin a portion with low weatherability and corrosionresistance and accordingly the resulting modified epoxy resin had nosufficient weatherability and corrosion resistance; meanwhile when theamount of the plasticity-modifying agent is decreased in order tofortify the weatherability and corrosion resistance, no high-buildcoatability is obtained.

A major object of the present invention is to provide a coating resincomposition having high-build coatability and further havingweatherability, corrosion resistance, flexibility, adhesion tosubstrate, etc. in good balance.

Another object of the present invention is to provide a cationicelectrocoating resin composition having such properties.

Other objects and advantages of the present invention will becomeapparent from the following description.

According to the present invention there is provided a coating resincomposition comprising, as a main component, an amino group-containing,modified epoxy resin derivative obtained by subjecting a hydroxylgroup-containing epoxy resin having an epoxy equivalent of 200-400 and acyclic ester compound represented by the general formula (I) ##STR2## (Ris a hydrogen atom or a methyl group and n is 3-6) to an additionreaction to obtain an addition product and then adding to the additionproduct a polyphenol compound and an amino group-containing compound.

The amino group-containing, modified epoxy resin derivative of thepresent invention has high-build coatability and is superior inweatherability, corrosion resistance and flexibility. This is thought tobe because the amino group-containing, modified epoxy resin derivativehas a structure having a highly reactive primary hydroxyl group at theside chain, which has been obtained by introducing into a hydroxylgroup-containing epoxy resin a cyclic ester compound of highplasticizing ability in a ring-opening state.

The coating resin composition of the present invention is described inmore detail below.

The amino group-containing, modified epoxy resin derivative is obtainedby subjecting a hydroxyl group-containing epoxy resin of certain typeand a cyclic ester compound represented by the general formula (I) to anaddition reaction to obtain an addition product and then adding to theaddition product a polyphenol compound and an amino group-containingcompound.

The hydroxyl group-containing epoxy resin used in the production of theabove amino group-containing, modified epoxy resin derivative is acompound having, on an average, hydroxyl groups of at least 0.5,preferably 0.7 to less than 2, more preferably 0.8 to 1.5 per moleculeand epoxy groups of 2 or more, preferably 2 to 3 per molecule. There isparticularly preferred a polyepoxy compound having 2 epoxy groups permolecule. The epoxy resin has an epoxy equivalent of 200-400, preferably220-350, more preferably 230-280 and has a molecular weight ofordinarily about 400 to about 1,000, preferably about 400 to about 700,more preferably about 450 to about 600. Particularly useful polyepoxycompounds include a polyglycidyl ether of a polyphenol such as bisphenolA. As typical examples of such a polyepoxy compound, there can bementioned glycidyl ethers of polyphenols such asbis(4-hydroxyphenyl)-2,2-propane, bis(4-hydroxyphenyl)-1,1-ethane,bis(4-hydroxyphenyl)-methane, 4,4'-dihydroxydiphenylsulfone, phenolicnovolak, cresol novolak and the like, as well as their polymers.

In the present invention, the hydroxyl group-containing epoxy resin issubjected to an addition reaction with the cyclic ester compoundrepresented by the general formula (I). This addition reaction can beeffected according to a per se known method. It can be effected, forexample, by heating the hydroxyl group-containing epoxy resin and thecyclic ester compound at a temperature of about 100° C. to about 250° C.for about 1 hour to about 15 hours in the presence of a metal compoundas a catalyst such as titanium compound (e.g. tetrabutoxytitanium,tetrepropoxytitanium), organotin compound (e.g. tin octylate, dibutyltinoxide, dibutyltin laurate), stannous chloride and the like. It isconvenient that the catalyst be generally used in an amount of 0.5-1,000ppm based on the total amount of the hydroxyl group-containing epoxyresin and the cyclic ester compound.

The cyclic ester compound is represented by the general formula (I)##STR3## (R is a hydrogen atom or a methyl group and n is 3-6). As thecyclic ester compound, there can be mentioned, for example,δ-valerolactone, ε-caprolactone, ξ-enantholactone, η-caprylolactone,γ-valerolactone, δ-caprolactone, ε-enantholactone and ξ-caprylolactone.Particularly preferred are those cyclic ester compounds (lactones) ofthe general formula wherein n is 4-6 and R is a hydrogen atom (i.e. 6-8carbon atoms).

In the addition reaction between the hydroxyl group-containing epoxyresin and the cyclic ester compound of the formula (I), the cyclic estercompound causes ring opening and reacts with the secondary hydroxylgroup in the epoxy resin to produce a primary hydroxyl group and at thesame time the methylene chain portion of the lactone endows the epoxyresin with flexibility, high-build coatability and weatherability Theamount of the cyclic ester compound of the formula (I) to be reactedwith the epoxy resin has no strict restriction but it is generallypreferable that the cyclic ester compound be used so that the finalreaction product of the present invention, i.e. the aminogroup-containing, modified epoxy resin derivative contains a portionbased on the cyclic ester compound in an amount of 5-50% by weight,preferably 10-40% by weight, more preferably 15-35% by weight.

In the present invention, to the addition reaction product (hereinafterreferred to as "lactone-modified epoxy resin") between the hydroxylgroup-containing epoxy resin and the cyclic ester compound are furtheradded a polyphenol compound and an amino group-containing compound toobtain an amino group-containing, modified epoxy resin derivative. Theorder of the addition reaction of the lactone-modified epoxy resin withthe polyphenol compound or the amino group-containing compound has norestriction. It is possible to first conduct the reaction with thepolyphenol compound, or to conduct, prior to that reaction, the reactionwith the amino group-containing compound, or to simultaneously conductthe reaction with the polyphenol compound and the reaction with theamino group-containing compound.

When the amino group-containing, modified epoxy resin derivative isdesired to have a narrow molecular weight distribution, it isadvantageous that the polyphenol compound is added to thelactone-modified epoxy resin and then the amino group-containingcompound is reacted.

The polyphenol compound used in the present invention includes, forexample, bis(4-hydroxyphenyl)-2,2-propane,bis(4-hydroxyphenyl)-1,1-ethane, bis(4-hydroxyphenyl)-1,1-isobutane,4,4'-dihydroxybenzophenone, bis(4-hydroxy-3-t-butylphenyl)-2,2-propane,bis(2-hydroxynaphthyl)methane, 1,5-dihydroxynaphthalene, etc.

The reaction of the polyphenol compound with the lactone-modified epoxyresin or with the addition product between the lactone-modified epoxyresin and the amino group-containing compound can be effected accordingto a per se known method. It can be effected, for example, by heating(a) the polyphenol compound and (b) the lactone-modified epoxy resin orthe addition product between the lactone-modified epoxy resin and theamino group-containing compound at a temperature of about 50° C. toabout 200° C. for about 1 hour to about 15 hours in the presence of1-2,000 ppm, based on the total amount of (a) and (b), of a catalystsuch as a basic tertiary amino compound (e.g. dimethylbenzylamine,tributylamine, triethylamine).

By this reaction, the polyphenol compound is added to and introducedinto the lactone-modified epoxy resin or the addition product havingepoxy groups between the lactone-modified epoxy resin and the aminogroup-containing compound, whereby a secondary hydroxyl groupcontributing to adhesitivity can be formed in the resulting product.

In the above reaction, the amount of the polyphenol compound used is notrestricted strictly, but it is advisable that the amount be generally0.2-0.9 mole, preferably 0.35-0.80 mole, more preferably 0.5-0.75 moleper mole of the lactone-modified epoxy resin or the addition productbetween the lactone-modified epoxy resin and the amino group-containingcompound.

As the amino group-containing compound which can be reacted with thelactone-modified epoxy resin or with the addition product between thelactone-modified epoxy resin and the polyphenol compound, there can bementioned, for example, aliphatic, alicyclic or aromatic-aliphaticprimary or secondary amines (these compounds form amino groups byreacting with the epoxy group of the epoxy resin), as well as tertiaryaminomonoisocyanates obtained by the reaction between a tertiaryaminoalcohol and diisocyanate (these isocyanates can introduce aminogroup into the epoxy resin by reacting with the hydroxyl group of theepoxy resin).

As examples of the primary or secondary amines, there can be mentionedthe followings.

(1) Primary monoamines such as alkylamine (e.g. methylamine, ethylamine,n- or iso-propylamine) and monoalkanolamine (e.g. monoethanolamine, n-or iso-propanolamine).

(2) Secondary monoamines such as dialkylamine (e.g. diethylamine),dialkanolamine (e.g. diethanolamine, di-n- or di-iso-propanolamine) andN-alkylalkanolamine (e.g. N-methylethanolamine, N-ethylethanolamine).

(3) Primary or secondary polyamines such as ethylenediamine,diethylenetricamine, hydroxyethylaminoethylamine, ethylaminoethylamine,methylaminoporpylamine, dimethylaminoethylamine anddimethylaminopropylamine.

As examples of the tertiary aminomonoisocyanates, there can be mentionedthe followings: teritary monoaminoisocyanates obtained by the reactionof (a) a tertiary aminoalcohol such as 2-(dimethylamino)ethanol,N,N-diisopropylethanolamine, 2-(di-n-butylamino)ethanol,2-(diethylamino)ethanol, 1-(diethylamino)-2-propanol,3-(diethylamino)-1-propanol, 3-(dimethylamino)-1-propanol or the likeand (b) a polyisocyanate such as hexamethylene diisocyanate, isophoronediisocyanate, hydrogenated diphenylmethane diisocyanate, tolylenediisocyanate, diphenylmethane-4,4'-diisocyanate or the like. The abovereaction can be effected preferably in an about equimolar relationship.

Of the above amino group-containing compounds, particularly preferableare monoethanolamine, diethanolamine, diethylenetriamine,hydroxyethylaminoethylamine, N-methylethanolamine anN-ethylethanolamine.

The above primary or secondary amines can be reacted, as they are, withthe epoxy group in the lactone-modified epoxy resin or in the additionproduct between the lactone-modified epoxy resin and the polyphenolcompound under conditions such as about 30°-150° C. × about 1-3 hours.However, when a primary amine or a N-hydroxyalkyl secondary amine suchas dialkanolamine or N-alkylalkanolamine is used, it is preferable thatthe amine be firstly reacted with a ketone, an aldehyde or a carboxylicacid at, for example, about 100°-230° C. to convert to a ketimine, aaldimine, an oxazoline or an imidazoline and this reaction product bereacted with the lactone-modified epoxy resin or the addition productbetween the lactone-modified epoxy resin and the polyphenol compoundunder conditions such as about 80°-200° C. × about 2-5 hours.

When a tertiary aminomonoisocyanate is used as the aminogroup-containing compound, it can be reacted with the lactone-modifiedepoxy resin or the addition product between the resin and the polyphenolcompound at a temperature of, for example, about 30°-150° C. until thereremains no isocyanate group when measured by the IR absorption spectrum.

The amino group-containing compound is used preferably in such an amountthat the final reaction product of the present invention, i.e. the aminogroup-containing, modified epoxy resin derivative has an amine value ofgenerally 15-100, preferably 30-80, more preferably 35-60. When theamine value is less than 15, it is difficult to disperse the finalreaction product in water. When the amine value is more than 100, thecoating film of the final reaction product tends to have poor waterresistance.

It is preferred that the thus obtained amino group-containing, modifiedepoxy resin derivative have a weight-average molecular weight ofgenerally about 1,000-8,000, preferably about 1,500-6,000, morepreferably about 2,000-5,000.

The amino group-containing, modified epoxy resin derivative can be usedin combination with an external crosslinking agent, as necessary. As theexternal crosslinking agent usable in the present invention, there canbe mentioned compounds having at least two crosslinkable groups in themolecule, such as blocked polyisocyanate, α-hydroxycarbamic acid esterof polyamine, malonic acid ester derivative, methylolatedmelamine,methylolated urea, polyepoxy compound, compound containingα,β-unsaturated double bonds and the like. It is preferable that thecompounding ratio (as solid content) of the amino group-containing,modified epoxy resin derivative and the external crosslinking agent beordinarily 100/0 to 50/50, preferably 90/10 to 60/40 by weight.

It is also possible that the amino group-containing, modified epoxyresin derivative be reacted with a partially-blocked polyisocyanatecompound to convert to a self-crosslinkable coating resin composition.

The partially blocked polyisocyanate compound used in the above reactionis a compound which has a blocked ratio of 20-90%, preferably 30-80%,more preferably 40-75% and which can be obtained by reacting apolyisocyanate compound with an isocyanate-blocking agent in suchproportions that the ratio of the number of isocyanate groups inpolyisocyanate compound/the number of active hydrogen atoms inisocyanate-blocking agent becomes 5/1 to 10/9, preferably 10/3 to 5/4,more preferably 5/2 to 4/3. Herein, the blocking degree refers to aproportion of the number of blocked isocyanate groups to the number ofall isocyanate groups originally present in polyisocyanate when theisocyanate groups in said polyisocyanate are reacted with the activehydrogen atoms in blocking agent.

The above reaction can be conducted ordinarily in a solvent-free stateor in a solvent inert to the reaction at a temperature of about 10°-15°C. In view of the quality of partially blocked polyisocyanate compoundobtained and the controllability of the reaction, it is particularlypreferable that the reaction be effected while dropping anisocyanate-blocking agent or its solution in an inert solvent, into apolyisocyanate per se or its solution in an inert solvent, at 20°-110°C.

As the polyisocyanate compound, there can be mentioned, for example,aliphatic or alicyclic polyisocyanate compounds such as hexamethylenediisocyanate, isophorone diisocyanate, hydrogenated diphenylmethanediisocyanate and the like, as well as aromatic polyisocyanate compoundssuch as tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate and thelike. These compounds can be used alone or in combination of two ormore.

Of the above polyisocyanate compounds, preferable are aliphatic oralicyclic diisocyanate compounds, particularly hexamethylenediisocyanate and isophorone diisocyanate in view of the weatherabilityof cured coating film.

The isocyanate-blocking agent adds to the isocyanate group of thepolyisocyanate compound and thereby blocks the isocyanate group. Thepartially blocked polyisocyanate compound formed by the addition isrequired to be stable at room temperature and, when heated to about120°-250°C., particularly about 130°200°C., to produce free isocyanategroup by liberating the blocking agent. As the blocking agent satisfyingsuch requirements, there can be mentioned, for example, lactam compoundssuch as ε-caprolactam, γ-butyrolactam and the like; oxime compounds suchas methyl ethyl ketoxime, cyclohexanone oxime and the like; phenolcompounds such as phenol, para-t-butylphenol, cresol and the like;aliphatic alcohols such as n-butanol, 2-ethylhexanol and the like;aromatic alkyl alcohols such as phenylcarbinol, methylphenylcarbinol andthe like; and ether alcohol compounds such as ethylene glycol monobutylether and the like.

Of these blocking agents, those of oxime or lactam type are particularlypreferable in view of the curability of coating film because they can beliberated at relatively low temperatures.

The reaction of the amino group-containing, modified epoxy resinderivative with the partially blocked polyisocyanate compound can beeffected ordinarily at about 50°-150°C., particularly about 60°-120° ina nitrogen current until there remains substantially no isocyanategroup. In this reaction, the ratio (weight ratio of solid content) ofthe amino group-containing, modified epoxy resin derivative and thepartially blocked polyisocyanate compound is generally 20/1 to 3/5,preferably 10/1 to 4/5, more preferably 9/1 to 5/5.

The amino group-containing, modified epoxy resin derivative or thereaction product between said resin derivative and the partially blockedpolyisocyanate compound can be used as a film-forming component incoating resin compositions. It can be advantageously used in cationicelectrocoating resin compositions, in particular.

When the amino group-containing, modified epoxy resin derivative or thereaction product between said resin derivative and the partially blockedpolyisocyanate compound is used in a cationic electrocoating resincomposition, said resin derivative or said reaction product can be madeinto an aqueous solution or aqueous dispersion. This aqueous solution oraqueous dispersion can be obtained according to a per se known method.For example, the resin derivative or the reaction product between thisresin derivative and the partially blocked polyisocyanate compound isneutralized with at least one of appropriate acids such as inorganicacids (e.g. boric acid, phosphoric acid, sulfuric acid, hydrochloricacid) and organic acids (e.g. lactic acid, acetic acid, formic acid);water is added thereto with thorough stirring; thereby, theneutralization product can be stably dissolved or dispersed in water.

The amount of acid required for neutralization can not be specifiedstrictly. However, in view of electrocoatability, it is preferable thatthe amount in terms of neutralization number be about 5-40 mg KOH,particularly 10-20 mg KOH per g of resin solid content.

Into the thus prepared aqueous solution or aqueous dispersion can beincorporated as necessary, by kneading, colored pigments such as carbonblack, titanium white, red iron oxide and the like; fillers such asclay, talc and the like; rust-preventive pigments such as strontiumchromate, lead chromate and the like; and other additives. As otheradditives, there can be mentioned, for example, nonionic surfactants asa dispersant or as an agent for prevention of cissing on coatingsurface; curing accelerators (e.g. salts of metals such as lead,bismuth, tin, zinc, iron, aluminum and the like, and/or imidazolinecompounds, imidazoles, phosphines, quaternary phosphonium salts); andwater-miscible organic solvents (e.g. ethylene glycol monobutyl ether,ethylene glycol monoethyl ether, methoxypropanol, diethylene glycolmonoethyl ether, ethylene glycol monohexyl ether, ethylene glycol2-ethylhexyl ether, benzyl alcohol, octyl alcohol).

The above prepared aqueous solution or aqueous dispersion can be appliedto electrocoating using a method and apparatus per se knownconventionally in electrocoating. In this case, it is desirable that anarticle to be coated be used as a cathode and a stainless steel orcarbon plate be used as an anode. The electrocoating conditions have noparticular restrictions. However, desirably the electrocoating iseffected generally under conditions of 20°-30° C. (bath temperature),100-400 V, preferably 200-300 V, 0.01-3 A/dm² (current density), 1-5minutes (time of voltage application), 2/1 to 1/2 (areal ratio of anodeand cathode) and 10-100 cm (cathode-to-anode distance) with stirring.

The coating film formed on the cathode (the article to be coated) iswashed and then cured by baking ordinarily at about 120°-200°C.,preferably about 130°-180° C. for about 10-60 minutes, whereby a curedcoating film with excellent film properties can be obtained.

The coating resin composition, particularly the cationic electrocoatingresin composition of the present invention having the above mentionedconstitution has high-build coatability and is superior inweatherability, corrosion resistance, and flexibility because itcontains in the molecule a methylene side chain with a primary hydroxylgroup formed by the reaction of a hydroxyl group-containing epoxy resinand a cyclic ester compound. Further, said resin composition is superiorin water resistance, secondary adhesion and corrosion resistance becauseit contains a secondary hydroxyl group formed by the reaction of (a) alactone-modified epoxy resin or its addition product with an aminogroup-containing compound with (b) a polyphenol compound and beingeffective for adhesion to metal substrates. Accordingly, said resincomposition can be widely used in fields such as primer coating forautomotive body and coating for industrial parts and household electricappliances.

The present invention is described more specifically below by way ofExamples.

In the Examples, parts and % refer to parts by weight and % by weight,respectively.

PRODUCTION EXAMPLE 1 Production of Amino Group-Containing, ModifiedEpoxy Resin Derivative

Into a flask equipped with a stirrer, a thermometer, a nitrogen-blowingtube and a reflux condenser was fed 518 parts of an epoxy resin having anumber-average molecular weight of 370 and an epoxy equivalent of 185obtained by the reaction of bisphenol A and epichlorohydrin. Theretowere added 57 parts of bisphenol A and 0.2 part of dimethylbenzylamine,and the mixture was reacted at 120° C. until an epoxy equivalent of 250was obtained. Then, 213 parts of ε-caprolactone and 0.03 part oftetrabutoxytitanium and the resulting mixture was heated to 170°C. Withthis temperature being kept, sampling was conducted with the lapse oftime to trace the amount of unreacted ε-caprolactone by the measurementof the IR absorption spectrum. When the conversion of raw materialsbecame 98% or higher, 148 parts of bisphenol A and 0.4 part ofdimethylbenzylamine were further added and the resulting mixture wasreacted at 130° C. until an epoxy equivalent of 936 was obtained. Then,257.4 parts of methyl isobutyl ketone, 25.6 parts of diethylamine and68.3 parts of diethanolamine were added and the resulting mixture wasreacted at 80° C. for 2 hours. The reaction mixture was diluted with143.4 parts of ethylene glycol monobutyl ether to obtain an aminogroup-containing, modified epoxy resin derivative having a resin solidcontent of 72% and an amine value (of resin solid content) of 54.5.

PRODUCTION EXAMPLE 2 Production of Amino Group-Containing, ModifiedEpoxy Resin Derivative

Into a flask equipped with a stirrer, a thermometer, a nitrogen-blowingtube and a reflux condenser were fed 518 parts of an epoxy resin havinga number-average molecular weight of 370 and an epoxy equivalent of 185obtained by the reaction of bisphenol A and epichlorohydrin. Theretowere added 57 parts of bisphenol A and 0.2 part of dimethylbenzylamine,and the mixture was reacted until an epoxy equivalent of 250 wasobtained. 270 parts of ε-caprolactone and 0.03 part oftetrabutoxytitanium were added and the mixture was heated to 170°C. Withthis temperature being kept, sampling was conducted with the lapse oftime to trace the amount of unreacted ε-caprolactone by the measurementof the IR absorption spectrum. When the conversion of raw materialsbecame 98% or higher, 148 parts of bisphenol A and 0.4 part ofdimethylbenzylamine were further added and the mixture was reacted at130° C. until an epoxy equivalent of 993 was obtained. Thereto was added138 parts of a methyl isobutyl ketone solution of a ketimine betweenmonoethanolamine and methyl isobutyl ketone (the amount of effectivecomponent in solution=80%), and the mixture was reacted at 140° C. untilan epoxy equivalent (of resin solid content) of 4797 was obtained. Thereaction mixture was diluted with 248 parts of ethylene glycol monobutylether and, when the temperature became 100°C., there was added 50 partsof a methyl isobutyl ketone solution of a ketimine betweendiethylenetriamine and methyl isobutyl ketone (the amount of effectivecomponent in solution=80%). The mixture was reacted at 100° C. untilthere remained no epoxy group, to obtain an amino group-containing,modified epoxy resin derivative having a resin solid content of 80% andan amine value (of resin solid content) of 52.5.

PRODUCTION EXAMPLE 3 Production of Amino Group-Containing, ModifiedEpoxy Resin Derivative for Comparative Example 1

Into the same reactor as used in Production Example 1 were fed, withnitrogen gas being blown in, 476 parts of a polypropylene glycoldiglycidyl ether having an epoxy equivalent of about 317, 342 parts ofbisphenol A and 36 parts of a methyl isobutyl ketone solution of aketimine between monoethanolamine and methyl isobutyl ketone (the amountof effective component in solution=80%). The mixture was reacted at 160°C. until there remained no epoxy group.

Thereto were added 665 parts of bisphenol A diglycidyl ether having anepoxy equivalent of about 190 and 232 parts of a methyl isobutyl ketonesolution of a kitimine between monoethanolamine and methyl isobutylketone (the amount of effective component in solution=80%). The mixturewas reacted at 140° C. until an epoxy equivalent (of resin solidcontent) of 3555 was obtained. The resulting mixture was diluted with365 parts of ethylene glycol monobutyl ether. When the temperature camedown to 100°C., there was added 100 parts of a methyl isobutyl ketonesolution of a diketimine between diethylenetriamine and methyl isobutylketone (the amount of effective component in solution=80%). The mixturewas reacted at 100° C. until there remained no epoxy group, to obtain anamino group-containing epoxy resin derivative having a resin solidcontent of 80% and an amine value (of resin solid content) of 66.3.

PRODUCTION EXAMPLE 4 Production of Amino Group-Containing, ModifiedEpoxy Resin Derivative for Comparative

Example 2

Into the same reactor as used in Production Example 1 were fed, withnitrogen gas being blown in, 1,110 parts of an epoxy resin having anumber-average molecular weight of 370 and an epoxy equivalent of 185obtained by the reaction of bisphenol A and epichlorohydrin, 495 partsof a polycaprolactonediol having a molecular weight of 550 [PLACCEL 205,product of Daicel Chemical Industries, Ltd.] and 3.02 parts ofdimethylbenzylamine. The mixture was reacted at 150° C. until an epoxyequivalent of 383 was obtained. Then, 251 parts of bisphenol A was addedand the resulting mixture was reacted at 120° C. until an epoxyequivalent of 928 was obtained. Thereafter, there was added 227 parts ofa methyl isobutyl ketone solution of a ketimine between monoethanolamineand methyl isobutyl ketone (the amount of effective component insolution=80%), and the mixture was reacted at 120° C. until an epoxyequivalent (of resin solid content) of 4617 was obtained. The reactionmixture was diluted with 464 parts of ethylene glycol monobutyl ether.When the temperature came down to 100°C., there was added 100 parts of amethyl isobutyl ketone solution of a ketimine between diethylenetriamineand methyl isobutyl ketone (the amount of effective component insolution=80%), and the mixture was reacted at 100° C. until thereremained no epoxy group, to obtain an amino group-containing epoxy resinderivative having a resin solid content of 80% and an amine value (ofresin solid content) of 55.9.

EXAMPLES 1-2 AND COMPARATIVE EXAMPLES 1-2

Each of the four resin solutions obtained in the above ProductiveExamples was mixed with methyl ethyl etoxime-blocked isophoronediisocyanate so that the blocked isocyanate group became equivalent tothe total amount of the primary hydroxyl group and the primary aminogroup both present in the epoxy-polyamine resin.

To 100 parts by weight (as solid content) of each of the resulting resincompositions were added 1 part of a polypropylene glycol (SANNIX PP4000, product of Sanyo Chemical Industries, Ltd.), 0.96 part of aceticacid and 1 part of lead acetate. The mixture was heated to 60° C. anddeionized water was slowly added with stirring to disperse the mixturein water to obtain an emulsion of good stability having a resin solidcontent of 30%.

To 100 parts by weight (as resin solid content) of each of the emulsionswere added 3 parts of basic lead silicate, 13 parts of titanium white,0.3 part of carbon black, 3 parts of clay, 2 parts of dibutyltin oxideand 1 part of a nonionic surfactant (Noigen 142 B, product of Dai-ichiKogyo Seiyaku Co., Ltd.). The mixture was treated in a ball mill todisperse the pigments until particle sizes of 10 μm of below wereobtained. The resulting dispersion was further diluted with deionizedwater until the resin solid content became 15%.

Using each of the four dilute paints obtained above, there was conductedthe cationic electrocoating of an untreated steel plate of a Bt-3080(zinc phosphate) -treated steel plate for 3 minutes at a bathtemperature of 28° C. at 250 V. Each of the electrocoated plates wassubjected to baking for 20 minutes at 160° C. and then tested forcorrosion resistance.

The resin composition and the test results are shown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________                                 Comparative                                                           Examples                                                                              Examples                                                              1   2   1   2                                            __________________________________________________________________________    Resin compounding                                                             Basic resin                                                                   Type (No. of Production Example)                                                                   1   2   3   4                                            Solid content (parts)                                                                              74  79  81  83                                           Methyl ethyl ketoxime - blocked isophorone                                                         26  21  19  17                                           diisocyanate, solid content (parts)                                           Film thickness*.sup.1 (μm)                                                                      43  48  45  21                                           Condition of coating film surface                                                                  ◯                                                                     ◯                                                                     ◯                                                                     ◯                                Corrosion resistance                                                          Untreated steel plate                                                         Resistance to salt spray*.sup.2, 480 hr (mm)                                                       1.2 1.9 4.5 4                                            Resistance to salt water immersion*.sup.3, 480 hr                                                  ◯                                                                     ◯                                                                     X   Δ                                      BT-3080-treated steel plate                                                   Resistance to salt spray*.sup.2,                                              1,000 hr (mm)        <1  <1  5-6 4-5                                          1,500 hr (mm)        1-2 1-2 --  --                                           Resistance to salt water immersion*.sup.3, 800 hr                                                  ⊚                                                                  ⊚                                                                  Δ                                          __________________________________________________________________________

In table 1, each *-marked test item denotes the following.

*1 Film thickness

A thickness of an electrocoating film formed when electrocoating waseffected using an untreated steel plate as cathode at 250 V for 3minutes.

*2 Resistance to salt spray

On an electrocoating film formed on a substrate were made cross cutswith a knife so that the cuts reached the substrate. Then, the substratehaving crosscut film was subjected to a test specified by JIS Z 2371 tomeasure the width of the rust and blister developed from the cross cuts.The test time was 480 hours for untreated steel plates and 1,000 and1,500 hours for Bt-3080-treated steel plates.

*3 Resistance to salt water immersion

A plate with an electrocoating film was immersed in a 5% aqueous NaClsolution, and the change in the flat portion of the plate was observed.The immersion time was 480 hours for untreated steel plates and 800hours for Bt-3080-treated steel plates.

The following rating criterion was used.

⊚: Substantially no change.

◯: A change is seen on the electrocoating film but the total of theblister and peeling is less than 5%.

○Δ : The total of the blister and peeling is 5% to less than 10%.

Δ: The total of the blister and peeling is 10% to less than 50%.

X: The total of the blister and peeling is 50% and more.

PRODUCTION EXAMPLE 5 Production of Amino Group-Containing, ModifiedEpoxy Resin

Into the same flask as used in Production Example 1 were fed 500 partsof an epoxy resin having a number-average molecular weight of 370 and anepoxy equivalent of 185 obtained by the reaction of bisphenol A andepichlorohydrin and 59.3 parts of bisphenol A. Thereto was added 0.2part of dimethylbenzylamine. The mixture was reacted at 130° C. until anepoxy equivalent of 256 was obtained. Then, 145.5 parts ofε-caprolactone and 0.08 part of tetrabutoxytitanium were added. Themixture was heated to 170°C. While keeping this temperature, samplingwas conducted with the lapse of time to trace the amount of unreactedε-caprolactone by the measurement of the IR absorption spectrum. Whenthe conversion of raw materials reached 98% or higher, there were added134.9 parts of methyl isobutyl ketone, 67.5 parts ofN-methylethanolamine and 36.4 parts of diethanolamine, and the resultingmixture was reacted for 2 hours at 80°C. Then, 490.2 parts of bisphenolA was added and the mixture was reacted at 120° C. until there remainedno epoxy resin. The reaction mixture was diluted with 176.5 parts ofmethyl ethyl ketone to obtain an amino group-containing, modified epoxyresin having a resin solid content of 75% and an amine value of 39.5.

PRODUCTION EXAMPLE 6 Production of Partially Blocked Polyisocyanate

222 parts of isophorone diisocyanate was fed into a reactor. Thereintowas slowly dropped 113.1 parts of methyl ethyl ketoxime with keeping thesystem temperature at 3°-40° C. by external cooling to synthesize apartially blocked polyisocyanate.

PRODUCTION EXAMPLE 7 Production of Partially Blocked Polyisocyanate

200 parts of hexamethylene diisocyanate was fed into a reactor.Thereinto was slowly dropped 155 parts of methyl ethyl ketoxime withkeeping the system temperature at 30°-40° C. by external cooling tosynthesize a partially blocked polyisocyanate.

PRODUCTION EXAMPLE 8 Production of Partially Blocked Polyisocyanate

200 parts of tolylene diisocyanate was fed into a reactor. Thereinto wasslowly dropped 169 parts of 2-ethylhexanol with controlling the systemtemperature at 80°-100° C. by cooling to synthesize a partially blockedpolyisocyanate.

PRODUCTION EXAMPLE 9 Production of Amino Group-Containing Epoxy Resinfor Comparative Example 3

Into the same flask as used in Production Example 1 was fed 600 parts ofan epoxy resin having a number-average molecular weight of 370 and anepoxy equivalent of 185 obtained by the reaction of bisphenol A andepichlorohydrin. Thereto were added 237.5 parts of bisphenol A and 0.93part of dimethylbenzylamine. The mixture was reacted at 120° C. in anitrogen current until an epoxy equivalent of 723 was obtained. Theretowere added 246.7 parts of ε-caprolactone and 0.05 part oftetrabutoxytitanium. The mixture was heated to 170°C. While keeping thistemperature, sampling was conducted with the lapse of time to trace theamount of unreacted ε-caprolactone by the measurement of the IRabsorption spectrum. When the conversion of raw materials reached 98% orhigher, there were added 298.1 parts of methyl isobutyl ketone, 29.7parts by weight of diethylamine and 79.1 parts of diethanolamine. Themixture was reacted for 2 hours at 80° C. The reaction mixture wasdiluted with 166.1 parts of methyl ethyl ketone to obtain a producthaving a solid content of 72% and an amine value of 54.6.

PRODUCTION EXAMPLE 10 Production of Amino Group-Containing Epoxy Resinfor Comparative Example 4

Into the same flask as used in Production Example 1 were fed 1,378.5parts of an epoxy resin having a number-average molecular weight of 370and an epoxy equivalent of 185 obtained by the reaction of bisphenol Aand epichlorohydrin and 621.5 parts of bisphenol A. Thereto was added546.9 parts of methyl isobutyl ketone. After the mixture was made into asolution by heating, 2.2 parts of dimethylbenzylamine was added. Theresulting mixture was reacted at 120° C. until an epoxy equivalent of1,000 was obtained. Then, 51.1 parts of diethylamine and 136.5 parts ofdiethanolamine were added and the mixture was reacted for 2 hours at80°C. The reaction mixture was diluted with 303.8 parts of methyl ethylketone to obtain a product having a solid content of 72% and an aminevalue of 51.3.

EXAMPLE 3

83.7 parts of the partially blocked isocyanate obtained in ProductionExample 6 was added to 500 parts of the amino group-containing, modifiedepoxy resin obtained in Production Example 1. The mixture was reacted at100° C. in a nitrogen current until there remained no isocyanate groupby the measurement of the IR absorption spectrum. The reaction mixturewas diluted with 143.1 parts of diethylene glycol monobutyl ether toobtain a resin composition for cationic electrocoating paint having asolid content of 70% and an amine value (of resin solid content) of44.2.

EXAMPLES 4-6 AND COMPARATIVE EXAMPLES 3-4

An amino group-containing, modified epoxy resin and a partially blockedisocyanate both shown in Table 2 were reacted in proportions shown inTable 2, in the same manner as in Example 3. The reaction mixture wasdiluted with diethylene glycol monobutyl ether so that the solid contentafter dilution became 70%, whereby resin compositions for cationicelectrocoating paint of Examples 4-6 and Comparative Examples 3-4 wereobtained. The amine values (of resin solid content) of thesecompositions are shown in Table 2.

                                      TABLE 2                                     __________________________________________________________________________                                          Comparative                                                   Examples        Examples                                                      3   4   5   6   3   4                                   __________________________________________________________________________    Materials                                                                     Amino group-containing modified epoxy resin                                   No. of Production Example                                                                           1   1   1   5   9   10                                  Parts                 500 500 500 480 500 500                                 Partially blocked polyisocyanate                                              No. of Production Example                                                                           6   7   8   6   6   6                                   Parts                 83.6                                                                              83.6                                                                              87.5                                                                              45.4                                                                              83.6                                                                              91.1                                Resin composition for cationic electropaint                                   Amine value (of resin solid content)                                                                44.2                                                                              44.2                                                                              43.8                                                                              35.1                                                                              44.3                                                                              40.9                                Solid content (%)     70  70  70  70  70  70                                  __________________________________________________________________________

APPLICATION EXAMPLE 1

57.1 parts of the resin composition for cationic electrocoating paintobtained in Example 3 was neutralized with 1.1 parts of glacial aceticacid. Thereto was added 41.8 parts of deionized water to disperse theresin composition in water to obtain a resin emulsion (I) having a solidcontent of about 40%.

An electrocoating paint having the following formulation waselectrocoated on a zinc phosphate-treated cold-rolled steel plate havinga thickness of 0.8 mm so that the coating film had a thickness of 20 μm.After water washing, the coated steel plate was baked at 180° C. for 30minutes. The resulting coated plate (test plate) was tested forproperties of coating film. The results are shown in Table 4.

    ______________________________________                                        Component       Amount (parts)                                                ______________________________________                                        Resin emulsion (I)                                                                            100                                                           Titanium white  10                                                            Basic lead silicate                                                                           2                                                             Carbon black    0.3                                                           Dibutyltin oxide                                                                              2                                                             Deionized water 207                                                           ______________________________________                                    

APPLICATION EXAMPLES 2-4 AND COMPARATIVE APPLICATION EXAMPLES 1-2

Electrocoating paints and coated plates of Application Examples 2-4 andComparative Application Examples 1-2 were obtained in the same manner asin Application Example 1 except that there were used the resincompositions for cationic electrocoating paint as shown in Table 3. Thetest results of the coated plates are shown in Table 4.

                                      TABLE 3                                     __________________________________________________________________________                                                     Comparative                                       Application Examples        Application Examples                              1      2      3      4      1      2                     __________________________________________________________________________    Resin composition for electrocoating                                                               Example 3                                                                            Example 4                                                                            Example 5                                                                            Example 6                                                                            Comparative                                                                          Comparative           paint                                            Example                                                                              Example 4             (No. of Example or Comparative Example)                                       __________________________________________________________________________

                                      TABLE 4                                     __________________________________________________________________________                                                 Comparative                                               Examples            Examples                         Test item Test method    3    4    5    6    3    4                           __________________________________________________________________________    Properties of                                                                 coating film                                                                  Appearance                                                                              Visual check   ◯                                                                      ◯                                                                      ◯                                                                      ◯                                                                      ◯                                                                      Δ**                   Adhesion  Cross cuts-peeling test by                                                                   100/100                                                                            100/100                                                                            100/100                                                                            100/100                                                                            100/100                                                                            100/100                               cellophane adhesive tape                                            Impact resistance*.sup.1                                                                Du Pont impact tester,                                                                       >50  >50  >50  >50  >50  40                                    500 g, 1/2 in. (cm)*.sup.1                                          Flexibility*.sup.2                                                                      Bending test (10 mmφ)*.sup.2                                                             ◯                                                                      ◯                                                                      ◯                                                                      ◯                                                                      ◯                                                                      X                           Secondary adhesion                                                                      Adhesion after immersion in                                                                  100/100                                                                            100/100                                                                            100/100                                                                            100/100                                                                             70/100                                                                             50/100                               hot water of 40° C. for 10 days                              Corrosion Width of cross cut portions                                                                  0.9  1.2  0.7  0.5  4.2  Above 5                     resistance*.sup.3                                                                       peeled when the cross cut por-                                                tions have been peeled by a                                                   cellophane tape after 480 hours                                               of a salt spray test (mm)*.sup.3                                    weatherability*.sup.4                                                                   Time of peeling in two-coat                                                                  320  320  160  340  190  40                                    clear system (hr)*.sup.4                                            Overall rating                                                                          weatherability ⊚                                                                   ⊚                                                                        ⊚                                                                        X                                     Corrosion resistance                                                                         ◯                                                                      ◯                                                                      ◯                                                                      ◯                                                                      Δ                                                                            X                           __________________________________________________________________________     **Formation of pin holes                                                 

In Table 4, each *-marked test item was tested as follows.

*1 Impact resistance

A test plate with a coating film was placed in a constanttemperature-constant humidity chamber of 20±1° C. and 75±2% for 24hours. Then, a Du Pont impact tester was provided with impact tool whichhas a fixed roundness at its tip, a ring-shaped anvil which matches tothat roundness and an apparatus which drops the weight from the fixedheight; the test plate was placed between the anvil and the impact toolwith the coating film directed upward; and a given weight was dropped onthe impact tool to measure the maximum height at which the impact of thedropping gave neither cracking nor peeling of coating film.

*2 Flexibility

A test plate with a coating film was placed in a constanttemperature-constant humidity chamber of 20±1° C. and 75±2% for 24 hoursand then bent around a rod having a defined diameter with the coatingfilm directed outside by 180° C. in 1-2 seconds. The case giving nodamage on the both surfaces at the bent portion was rated as ◯, and thecase giving damage such as cracking and peeling on at least either ofthe both surfaces at the bent portion was rated as X.

*3 Corrosion resistance

On a plate with a coating film was made cross cuts. Then, the plate wassubjected to a test specified by JIS Z 2371 for 480 hours. The cross cutportions were subjected to a cellophane adhesive tape peeling test andthe width of peeling was measured.

*4 Weatherability

On a test plate with a cured electrodeposition coating film was coatedan aminoalkyd clear paint at a thickness of 35 μm followed by baking at140° C. for 15 minutes. The resulting coated plate was placed in asunshine weatherometer for 20 hours and then immersed in water at 40° C.for 20 hours. Thereafter, cross cuts were made on the plate, and theplate was subjected to a peeling test with a cellophane adhesive tape.This procedure as one cycle was repeated and there was recorded a totaltime for which the plate was placed in the sunshine weatherometerwithout causing any peeling.

What we claim is:
 1. A coating resin composition comprising, an aminogroup-containing, lactone-modified epoxy resin derivative havingsecondary hydroxyl groups and an amine value of 15 to 100 obtained by(i)subjecting(A) a hydroxyl group-containing epoxy resin having an epoxyequivalent of 200 to 400, and (B) a cyclic ester compound represented bythe general formula ##STR4## wherein R is a hydrogen atom or a methylgroup, n is an integer of 3 to 6 to an addition reaction to obtain alactone-modified epoxy resin; and then (ii) reacting thelactone-modified epoxy resin with(C) a polyphenol compound and (D) anamino group-containing compound, wherein the amount of the polyphenolcompound (C) is 0.2 to 0.9 mole per mole of the lactone-modified epoxyresin or per mole of the addition product having epoxy groups betweenthe lactone-modified epoxy resin and the amino group-containingcompound.
 2. A composition according to claim 1, wherein the epoxyequivalent of the hydroxyl group-containing epoxy resins is 220-350. 3.A composition according to claim 1, wherein the hydroxylgroup-containing epoxy resins has hydroxyl groups of at least 0.5, toless than 2 per molecule, on an average.
 4. A composition according toclaim 1, wherein the hydroxyl group-containing epoxy resins has 2 epoxygroups per molecule.
 5. A composition according to claim 1, wherein thehydroxyl group-containing epoxy resins is a glycidyl ether of apolyphenol or a polymer thereof.
 6. A composition according to claim 1,wherein the cyclic ester compound (B) is selected from δ-valerolactone,ε-caprolactone, ξ-enantholactone, η-caprylolactone, γ-valerolactone,δ-caprolactone, ε-enantholactone and ξ-caprylolactone.
 7. A compositionaccording to claim 1, wherein the cyclic ester compound (B) is a lactoneof the formula (I) in which R is a hydrogen atom and n is 4-6.
 8. Acomposition according to claim 1, wherein the amino group-containing,lactone-modified epoxy resin derivative contains a component derivedfrom the cyclic ester compound in an amount of 5-50% by weight.
 9. Acomposition according to claim 1, wherein the polyphenol compound (C) isselected from bis(4-hydroxyphenyl)-2,2-propane,bis(4-hydroxyphenyl)-1,1-ethane, bis(4-hydroxyphenyl)-1,1-isobutane,4,4'-dihydroxybenzophenone, bis(4-hydroxy-3-t-butylphenyl)-2,2-propane,bis(2-hydroxynaphthyl)methane and 1,5-dihydroxynaphthalene.
 10. Acomposition according to claim 1, wherein the amino group-containingcompound (D) is selected from aliphatic, alicyclic or aromatic-aliphaticprimary or secondary amines and tertiary aminomonoisocyanates.
 11. Acomposition according to claim 1, wherein the amino group-containingcompound (D) is selected from monoethanolamine, diethanolamine,diethylenetriamine and hydroxyethylaminoethylamine.
 12. A compositionaccording to claim 1, wherein the amino group-containing, modified epoxyresin derivative has an amine value of 30-80.
 13. A compositionaccording to claim 1, wherein the amine group-containing, modified epoxyresin derivative has a weight-average molecular weight of about 1,000 toabout 8,000.
 14. A coated article obtained by coating an article withthe composition of claim
 1. 15. A composition according to claim 1,wherein the amount of the polyphenol compound (C) is 0.35 to 0.80 moleper mole of the lactone-modified epoxy resin or per mole of the additionproduct having epoxy groups between the lactone-modified epoxy resin andthe amino group-containing compound.
 16. A composition according toclaim 1, wherein the amino group-containing, lactone-modified epoxyresin derivative is obtained by first reacting the lactone-modifiedepoxy resin with the polyphenol compound (C) in an amount of 0.2 to 0.9mole of the polyphenol compound (C) per mole of the lactone-modifiedepoxy resin, and then reacting the addition product between thelactone-modified epoxy resin and the polyphenol compound (C) with theamino group-containing compound (D).